The present invention relates to a magnetic tape winder for winding a magnetic tape through a prescribed length onto a smaller-diameter tape winding member from a supply source of magnetic tape of final product width, rewinding a magnetic tape from a tape winding member onto another tape winding member, winding a magnetic tape of larger width than the magnetic tape of the source, or winding a plurality of magnetic tapes of the final product width after the tapes have been severed from a magnetic tape whose width is larger than the final product width.
A conventional process of manufacturing a magnetic tape such as an audio cassette tape, a video cassette tape, a memory tape or a broadcasting-quality video tape generally includes a step in which a magnetic tape of prescribed length is wound onto a smaller-diameter tape winding member such as a reel and a hub from a magnetic tape source containing a long magnetic tape, a step in which the magnetic tape wound on the tape winding member is rewound therefrom onto another tape winding member, a step in which a magnetic tape of larger width than the final product width is wound onto a source reel after being severed into tapes of the final product width, or a step in which a plurality of magnetic tapes each having a final product width are wound after they have been severed from a source tape whose width is larger than the final product width.
When the magnetic tape is wound onto the tape winding member in the tape winding step or the tape rewinding step, tape behavior such as vibration of the tape in the direction of the thickness thereof and vibration of the tape in the direction of width thereof tends to change in response to changes in the physical properties of the tape or those of the tape winding member so that the side edges of the magnetic tape wound on the winding member are not aligned. As a result, the appearance of the tape wound on the member is not good. This tendency becomes more pronounced as the speed of the tape being wound on the tape winding member increases. Not only is the appearance of the final product magnetic tape poor, but also the tape is likely to have improper winding characteristics or suffer damage at the side edge of the tape, thereby causing it to develop various problems such as deterioration of the electromagnetic conversion properties of the tape. If the magnetic tape is a video tape for high-density recording, in particular, the above-mentioned tendency is a very serious problem because an audio signal and a carrier signal are recorded on the tape near the side edges thereof.
For these reasons, the appearance of the magnetic tape wound in the tape winding step or the tape rewinding step has conventionally had to be inspected manually. However, such inspection is costly and time consuming, and therefore represents a significant problem.
Conventional "neat" winding mechanisms, as shown in FIGS. 13 and 14, have been employed to reduce the burden of inspection. FIGS. 13 and 14 show a magnetic tape, a tape winding member 2, and other elements in the vicinity thereof. In the conventional neat winding mechanism shown in FIG. 13, an endless flexible belt 11 made of rubber, polyimide or the like and revolvably supported by rollers 12, 13 and 14 is passed along the magnetic tape T to elastically push the magnetic side of the tape in the radial direction of the tape winding member 2 relatively strongly to make the appearance of the wound tape neat. In the other conventional neat winding mechanism shown in FIG. 14, a belt 15 made of a relatively soft nonwoven fabric or the like and laid between one flange of the tape winding member 2 and one side edge of the magnetic tape T is wound at a constant slow speed from a belt unwinding member 16 to a belt winding member 18 while being supported by a roller 17 so as to push the side edge of the tape relatively strongly to make the appearance of the wound tape good. However, since each of the belts 11 and 15 is in direct contact with the magnetic tape T, various problems such as the magnetic layer of the tape being scraped off or fibers of the nonwoven fabric adhering to the tape can cause dropout in the recorded signal on the tape. Also, an inappropriate pushing force acts on the tape causing it to deform or causing damage to the side edges, thus effectively making it impossible to use the mechanisms to wind the tape neatly and properly.
Moreover, because the mechanisms tend to wear quickly, they are disadvantageous with respect to cost and maintenance. Furthermore, since the mechanisms must be constructed so as to allow the tape winding member 2 to move between at least a working position and a nonworking position to allow belt replacement and changing of the tape winding member, the mechanisms are complicated and the replacement of the tape winding member is so time consuming as to hinder improvement of productivity.
Presently, two different cassette tape winding systems are in general use. One of them is a so-called open winding system in which a magnetic tape is wound by one of the conventional neat winding mechanisms and thereafter put in a cassette to constitute a finished product. In the other of the systems, termed an in-cassette winding system, a C-0 winding system or a V-0 winding system, a magnetic tape is wound at the last stage of assembly of the cassette. In the in-cassette winding system, as shown in FIGS. 15 and 16, components except the magnetic tape T are assembled in the body of the cassette 23, tape winding members 2 and 3 coupled to each other by a leader tape 10 are put in a tape winding position and a tape unwinding position, respectively, in the body of the cassette, screws are tightened to form an almost-completed final product (which is referred to as a V-0 or a C-0), the leader tape is pulled out and cut off by an in-cassette winder, the leading edge of the magnetic tape to be wound in the cassette body is joined to the cut-off end of one of the two portions of the leader tape, the cut-off end of the other of the leader tape portions is suction-held by a holder 22, the tape winding member 2 having the cut-off leader tape portion joined to the leading edge of the magnetic tape is rotated to wind the magnetic tape through a prescribed length of the winding member, the magnetic tape is thereafter cut off, and the cut-off trailing edge of the wound tape is joined to the cut-off edge of the other leader tape portion to thereby complete the final product.
In the in-cassette winding system, it is impossible to put a neat winding member in contact with the magnetic tape near the tape winding member as in each of the above-described conventional neat winding mechanisms. For that reason, the wound state of the magnetic tape depends on the physical properties thereof and the dimensional accuracies of the various components of the cassette. Thus, the wound state cannot easily be controlled. As a result, the ratio of the number of neatly wound magnetic tapes to that of unneatly wound magnetic tapes is low. In order to improve the wound state of the magnetic tape, it has been attempted to provide a roller 24 having an upper end and a lower flanges 25 at the inlet opening of the cassette to apply a force to the magnetic tape in the direction of the width thereof to push the tape toward one side of the cassette. However, if the pushing force is strong, the side edge of the magnetic tape is likely to be damaged by the flange 25 of the roller 24. If the force is weak, the wound state of the tape will be little improved.
Under such circumstances, a magnetic tape winder was recently disclosed in Japanese Unexamined Published Patent Application No. 51642/86 in which, as shown in FIG. 17, a winding reel 40 is composed of a winding core 41 and a flange 42, and at least one magnet 31 is provided around a winding drive shaft 30 removably coupled to the winding core so that the flange is located between the magnetic and the magnetic tape T being wound onto the reel.
Other previously disclosed magnetic tape winders have magnets 19e and 19f having magnetic poles on the tops and bottoms of the magnets, as shown in FIGS. 18 and 19.
Yet other magnetic tape winders have been proposed having a circular magnet assembly 19g, an annular magnet assembly 19h and a square magnet assembly 19i, as shown in FIGS. 20, 21 and 22, respectively. Each of the circular magnet assembly 19g and the annular magnet assembly 19h is composed of magnets radially divided from each other. The square magnet assembly 19i is composed of rectangular magnets divided from each other. The magnets of each of the magnet assemblies 19g, 19h and 19i are disposed in such a manner that the mutually adjacent magnets differ from each other in magnetic polarity. As a result, some of the lines of magnetic forces of the mutually adjacent magnets form closed loops, as shown in FIGS. 20 and 22, so that the magnetic intensity of each of the magnet assemblies is very high. However, the present applicant has found that the very high magnetic intensity of each of the magnet assemblies does not sufficiently serve to neatly wind a magnetic tape.
One of the reasons for this will now be described. FIG. 23 shows a magnetic tape T being wound under the influence of an annular magnet assembly 19h as shown in FIG. 20 composed of radially divided magnets. FIG. 24 is a sectional view of the annular magnet assembly 19h taken along a line A-A. The directions of lines i of magnetic force of the magnets are indicated by arrows. Since the lines i of magnetic force extend in the direction of width of the magnetic tape T, the force which the magnetic assembly 19h exerts on the magnetic tape within the wound portion thereof is mostly a downward tensile force acting parallel to the axis of a shaft 27, and the magnet assembly exerts no force or very little force on the tape in the direction of the thickness thereof. As a result, the frictional force acting between the wound layers of the magnetic tape T being wound is not strong enough to offset external forces such as vibration of the winding motor. For that reason, the magnetic tape T is likely to move irregularly due to such external forces so that the tape is not neatly wound in its end portion.
The other of the above-mentioned reasons will now be described. Since the magnet assembly 19h is composed of radially divided magnets, the side edge of a part of the magnetic tape T being wound is magnetized as a south pole by the north pole of one of the magnets of the assembly and attracted thereto. However, when the winding shaft or winding reel is thereafter rotated by an angle of 60.degree. , the side edge magnetized to the south pole is rotated to the south pole of the next magnet of the assembly (assuming the assembly contains six magnets equally divided from each other as shown in FIG. 23 and the assembly is not rotated). At that time, the side edge magnetized to the south pole is repulsed by the south pole of the magnet and then remagnetized to a north pole by the same magnets. This repulsion takes place six times during one rotation of the winding shaft, thus hindering the neat winding of the magnetic tape.
Although the annular magnet assembly 19h shown in FIG. 20 has been discussed above, the same description is applicable to the circular magnet assembly 19g shown in FIG. 21.
Winding a magnetic tape under the influence of the square magnet assembly 191 will now be described. Although the lines i of magnetic force of the magnets of the square magnet assembly 19i are oriented as shown in FIG. 22, the directions of the lines on a circle having its center on the axis of the winding shaft vary from place to place, and the magnetic forces act in the direction of thickness of the magnetic tape being wound around the winding shaft also vary from place to place around the circle. For that reason, the frictional force between the wound layers of the magnetic tape in some places is not made strong enough to offset external forces.